The invention resides in equipment which is designed to simulate infrared scenes for testing thermal sensors, in other words, for testing devices which respond to thermally emitted radiation. The art is replete with infrared simulators which produce static scenes which are derived from partially transparent filters placed in front of black bodies operating at temperatures to approximate an average scene temperature. This may be compared to a photographic slide projector. To change the range of the scene thus produced, zoom optical systems have been employed. In like manner, moving targets within a fixed scene are simulated by the use of small black bodies on an XY stage or other precision motion generating device. The scenes are optically combined using beam splitters to present composite scenes which include a background and movable targets. This scene is then presented to the sensor.
Another concept has been the use of heated pixels to generate infrared scene simulation. For the most part, attempts using this concept have been unsuccessful because of the creation of a poor fill factor. That is, much of the scene area is inactive and is taken up with electrical leads, leaving very little space for the generation of individual infrared energy.
Another problem with prior art heated pixel devices is what is known as thermal blooming or cross talk from one heated pixel to an unheated adjacent pixel. This creates a larger feature than that desired on a thermal trail.
Many attempts resulted from the use of planar technology wherein heater elements and their leads are deposited on a single substrate. The problems have not been mitigated even with the use of multilayer circuit boards and microcircuit photolithography.
The present invention solves these problems in the use of heated pixel technology. Each of the pixels are isolated one from another to eliminate thermal blooming. The planar technology is replaced by a three-dimensional assemblage of leads and control circuitry. Such supportive elements do not reside in the plane of the heated pixels.
An object of this invention is to produce a device for generating a dynamic infrared scene for the ground testing of various infrared sensors.
Another object of this invention is to generate the equivalent of an infrared moving picture, i.e., a scene which is actually dynamic.
Many infrared sensors operate at cryogenic temperatures against cryogenic backgrounds and movement in that environment complicates simulated design.
It is yet another object of this invention to produce a true temperature representation of each pixel in the scene by controlling the individual pixel temperature to a degree corresponding to the temperature of an object in an actual scene. The present invention is intended to produce an intensity of radiation emitted by a pixel at a constant temperature over an appreciable range by the judicious control of the electrical current applied to a pixel. The pixels lend themselves to precise current pulsing and pulse repetition rates.
It is contemplated that the present invention when controlled by a computer using appropriate software can depict a wide variety of scenes with interaction between the simulator and the sensor to show the scene observed by the sensor as the sensors field of use shifts due to simulated attitude changes and rate changes.